Block copolymers of a polyolefin and a polymer of a vinyl compound possess desirable properties of polyolefins and furthermore are expected to improve dye-affinity, hydrophilicity and miscibility with other resins. Thus, various processes for producing the block copolymers have been proposed. For example, one process comprises polymerizing olefins in the presence of a stereospecific catalyst, and thereafter polymerizing vinyl compounds in the presence of an alkylene oxide (Japanese Patent Publication Gazette No. 8679/1969). However, by this process, an alkylene oxide may be incorporated into the copolymer and thus this process is not advantageous. Another process comprises polymerizing olefins using an anionic catalyst and block-copolymerizing vinyl compounds in the presence of a radical initiator (Japanese Patent Publication Gazette Nos. 40055/1970 and 42385/1972). However, upon using a radical initiator, substantial amounts of homopolymers of vinyl compounds are produced as by-products and thus this process is also not advantageous.
We have found that block copolymers can be prepared very efficiently from a polymer of ethylene or propylene or their copolymers, with another .alpha.-olefin, and a polymer of an acrylic ester or a methacrylic ester, by adding certain organic phosphorus compounds or tertiary amines and organic halides to specific catalyst systems for polymerization of said olefins described above. Thus, the present invention was achieved.